patches-own [ potential visited? elevation isGround]

turtles-own [ path main? life ]

​

globals [

  screen-width

  terrain-noise

  random-terrain-offset

  min-pot

  max-pot

  column-elevations

  strike-heights

  ;; Sliders for controlling the noise strength, branch frequency, and new branch life

  ;; grain, branches, and branch-life are controlled by sliders

]

​

to setup

  clear-all

​

  set screen-width max-pxcor - min-pxcor + 1

  set strike-heights[]

  ;;set terrain-noise (random-float (2 * terrain-noise-strength)) - terrain-noise-strength

  set random-terrain-offset random-float screen-width

   setup-potential-field

  set min-pot min [potential] of patches

  set max-pot max [potential] of patches

  ;; experimental code-----------------------------------------------------------------

    let temp-x min-pxcor

    repeat screen-width

    [

      randomize-terrain-noise

      let wave sin(2 * peak-count * temp-x + random-terrain-offset)

      let temp-y min-pycor

      let random-elevation sea-level + (terrain-amplitude * wave) + terrain-noise

      repeat random-elevation [

        ask patch temp-x temp-y[

          set isGround true

          set potential max-pot

          set elevation pycor

        ]

        set temp-y (temp-y + 1)

      ]

      set temp-x (temp-x + 1)

    ]

  set column-elevations n-values screen-width [0]

  let diffusion-iterator min-pxcor

  repeat screen-width[

    let column-elevation 0

    ask patches with [pxcor = diffusion-iterator] [if isGround = true [set column-elevation (column-elevation + 1)]]

    ask patches with [pxcor = diffusion-iterator] [set potential (potential + column-elevation * column-elevation / 650 + column-elevation / 15)]

    set column-elevations replace-item (diffusion-iterator + max-pxcor) column-elevations column-elevation

    set diffusion-iterator (diffusion-iterator + 1)

  ]

  repeat 2 [diffuse potential 1.0]

​

  ;; Visualize potential gradient

  reset-atmosphere

​

  start-lightning-bolt

  reset-ticks

end

​

to setup-potential-field

  let noise-strength noise

  ask patches [

    let base (max-pycor - pycor)

    let temp-noise (ifelse-value (noise-strength = 0)

                [ 0 ]

                [ random-float noise-strength - noise-strength / 2 ])

    set potential base + temp-noise

  ]

end

​

to reset-atmosphere

  ask patches [

    set visited? false

    ifelse isGround [

      set pcolor 33

    ]

    [

      set pcolor scale-color blue potential min-pot max-pot

    ]

  ]

end

​

to start-lightning-bolt

  ;; Create main lightning bolt

  create-turtles 1 [

    ;; Set starting position

    setxy random-float 180 - 90 (max-pycor)

    set color white

    set path []

    set main? true

    set life 999

    ask patch-here [

      set pcolor white

      set visited? true

    ]

  ]

end

​

to go

  if not any? turtles [

    reset-atmosphere

    start-lightning-bolt

  ]

  ask turtles [

    ;; Branch lifespan

    if not main? [

      set life life - 1

      if life <= 0 [ die ]

    ]

​

    ;; Get downward-ish neighbors

    let neighbors-down neighbors with [

      pycor <= [pycor] of myself or pxcor != [pxcor] of myself

    ]

    let current-pot [potential] of patch-here

    let cands neighbors-down with [

      potential > current-pot and not visited?

    ]

​

    ;; If grain = 0, prefer directly below if possible

    let direct-down patch pxcor (pycor - 1)

    if noise = 0 and direct-down != nobody and not [visited?] of direct-down [

      move-to direct-down

    ]

    ;; Otherwise, pick the best neighbor (only if grain > 0 or other conditions)

    ifelse any? cands [

      let next ifelse-value (noise = 0) [

        max-one-of cands [potential]

      ] [

        max-one-of cands [potential + random-float 1.5]

      ]

      face next

      fd 1

    ] [

      ;; If no candidates and grain > 0, fallback slightly (only for main)

      if not any? cands and main? and pycor > min-pycor [

        set heading 180 + random 60 - 30

        fd 1

        ask patch-here [

          set pcolor white

          set visited? true

        ]

      ]

    ]

​

    ;; Update patch state

    ask patch-here [

      set pcolor white

      set visited? true

    ]

​

    ;; Branching logic — disabled when grain = 0

    if main? and noise > 0 [

      let depth-frac (pycor - min-pycor) / (max-pycor - min-pycor)

      let branch-chance branches * depth-frac

      if random-float 1.0 < branch-chance [

        hatch 1 [

          set color white

          set path []

          set main? false

          set life branch-life ;; Use branch-life slider to determine branch life

          rt random 120 - 60

          fd 1

          ask patch-here [

            set pcolor white

            set visited? true

          ]

        ]

      ]

    ]

​

    ;; Die if done or touching ground

    if [elevation] of patch-here != 0 or (not main? and not any? cands) [

      if main? [

        set strike-heights lput (pycor + 90) strike-heights

        set-current-plot "Lightning Strikes"

        set-current-plot-pen "strike-height"

        plot ycor + 90

        set-current-plot-pen "average-strike-height"

        plot mean strike-heights

      ]

      die

    ]

  ]

  tick

end

​

to randomize-terrain-noise

  set terrain-noise (random-float (2 * terrain-noise-strength)) - terrain-noise-strength

end

​

​

to reset-simulation

  clear-all

  setup

end

​